1. Field of the Invention
The present invention relates to an antilock brake system for an automobile adapted to prevent locking of the wheels of the automobile by adjusting the pressure of brake fluid when applying a quick brake or the brake on a slippery road, and more particularly to the structural characteristics of such an antilock brake system.
2. Statement of the Prior Art
There is devised as one of the systems to improve the safety of automobiles an antilock brake system adapted to prevent locking of the wheels of an automobile when applying a quick brake or the brake on a slippery road. Recently, as the demand for high-performance automobiles has been increasing, there is a tendency that many automobiles equipped with the aforesaid antilock brake system are produced.
A conventional antilock brake system will be described with reference to FIGS. 7 and 8.
FIG. 7 is a schematic explanatory view showing a conventional antilock brake system, and FIG. 8 is a diagram showing connections of electric wires.
As shown in FIG. 7, the conventional antilock brake system comprises rotation detectors 101 to 104, a hydraulic unit 105, an electronic unit 106, and a relay box 107, and the construction thereof will schematically be described as below.
The rotation detectors 101 to 104 are intended to detect the rotating conditions of wheels A to D, and are provided on the wheels A to D, respectively. The rotation detectors 101 to 104 each comprise sensors 101a to 104a, and sensor rotors 101b to 104b. The sensors 101a to 104a each are constituted by permanent magnets, coils, and pole pieces, and are mounted on the steering knuckles, with the front wheels, and on the hub spindles, with the rear wheels. The sensor rotors each comprise concaves and convexes (not shown) circumferentially arranged at equal intervals on the outer circumferences, and are mounted on the drive shafts, with the front wheels, and on the rear hubs, with the rear wheels.
Therefore, the sensor rotors 101b to 104b rotate integrally with the wheels A to D. The sensors 101a to 104a detect the rotating conditions of the wheels A to D by detecting the concaves and convexes on the outer circumferences of the sensor rotors 101b to 104b while the rotors are rotating. The rotation detectors 101 to 104 then send out detected signals to the electronic unit 106.
FIG. 8 is one example of connections of electric wires used in the conventional antilock brake system. The hydraulic unit 105 controls the pressure of brake fluid for the wheel cylinders by controlling the switching of four solenoid valves 105a to 105d, which is carried out based on control signals sent from the electronic unit 106. The hydraulic unit 105 has a motor 105e for driving a pump, not shown, for making brake fluid flow back to the master cylinder for applying pressure thereon.
The electronic unit 106 calculates the wheel speed and the acceleration and negative acceleration of the wheel on the basis of the detected signals sent from the rotation detectors 101 to 104 and estimates the vehicle speed, and monitors whether or not there exists any wheel that will be locked if the brake is applied in a state so calculated. In a case where the electronic unit 106 judges that there is or are wheels that will be locked, it then controls the solenoid valves 105a to 105d of the hydraulic unit 105 so as to reduce the brake fluid pressure with respect to the wheel cylinders of the wheels so judged. In a case where the electronic unit 106 judges that the locking of the relevant wheels is avoided, it then controls the switching of the solenoid valves 105a to 105d so as to increase the brake fluid pressure again.
The relay box 107 incorporates a motor relay 107a for switching on and off the motor 105e and a fail safe relay 107b for interrupting the power source for the solenoid valves 105a to 105d of the hydraulic unit 105 and the motor relay in the event that irregularity takes place in the antilock brake system.
In the conventional antilock brake system, as shown in FIG. 7, it is common practice that the hydraulic unit 105 and the relay box 107 are disposed in the engine compartment, while the electronic unit 106 is disposed under the seat or inside the front panel. As mentioned above, the rotation detectors 101 to 104 are mounted on the wheel portions. In FIG. 8, reference numeral 108 denotes a battery for the automobile, reference numeral 109 an ignition switch, reference numeral 110 a stop lamp switch disposed in the vicinity of the brake pedal, and reference numeral 111 a stop lamp constituting a part of the rear lamp.
In current automobiles, as the demand for high-performance automobiles has been increasing, the number of electronic units used also increases. On top of this, on many occasions securing of wider room space is demanded. However, when the electronic unit 106 is disposed in the passenger compartment as before, a large number of long wiring is required for electrically connecting this electronic unit 106 to the inside of the engine compartment, resulting in a drawback in that it is difficult to meet the demand for securing wider room space.
In addition, as in the case of the conventional antilock brake system, when the hydraulic unit 105 and the electronic unit 106 are separately installed in the engine compartment and the passenger compartment, respectively, a process of providing the aforesaid wiring harnesses for effecting electric connections between these two components is required, which creates a problem when trying to improve the manufacturing productivity of automobiles. In particular, in current automobiles, there is a tendency that not only the antilock brake system but also a lot of systems that have not been employed before are equipped on automobiles, which requires more wiring harnesses, making a wiring harness mounting operation complicated. In order to cope with the simplification of the process, it is desired to reduce the necessity of wiring.